Perforated armor plates

ABSTRACT

A system of armor plates is adapted for protection of a structure against projectiles B and S of two characteristic calibers D B  and D S , D B &gt;D S . The system compres a main armor plate and an auxiliary plate mounted in front of the main armor plate at a distance therefrom. The auxiliary plate comprises a plate made of ballistic material and perforated with through holes of characteristic diameter D, 1.2 D B &gt;D&gt;1.2 D S . At least one hard-material body of diameter D H  is disposed in each of the holes, such that the auxiliary plate provides at least destabilization of impacting projectiles S capable of free passage through an unobstructed hole of diameter D.

FIELD OF THE INVENTION

This invention relates to multi-layer ballistic armor and, particularly, to armor plates suitable for use as add-on (exterior) armor for military vehicles.

BACKGROUND OF THE INVENTION

Perforated or slit armor plates are in use for many years in armor systems where they are installed at some stand-off distance from the vehicle's basic armor. The use of those plates is mainly to effectively break an incoming projectile or at least to divert it from its incident trajectory and thus substantially reduce its residual penetration capability through the basic armor. The total weight of such armor system is considerably less than the weight of a basic armor with the same antiballistic capability. Usually the holes or slits are designed to interact with the characteristic diameter of the threat (projectile caliber), and the performance effectiveness of such armor under impact is dominated by the plate material and thickness.

U.S. Pat. No. 5,014,593 discloses perforated plate armor including outer and inner perforated steel plates and which have associated patterns of holes. The plates are spaced with respect to each other and with respect to the object to be protected. The patterns of holes of the perforated steel plates are offset with respect to each other to prevent straight line penetration. An inner backing plate is provided to stop any particles that might penetrate both perforated steel plates. Fillers and connectors space the outer and inner perforated steel plates and the backing plate with respect to each other.

U.S. Pat. No. 5,221,807 discloses a ballistic armor with front and rear layers, which are spaced from each other by a spacing layer. The front layer is made of ceramic material formed with blind holes, and it is designed to score impacting projectiles before they strike the rear layer, which functions as a main armor layer.

EP 0 699 887 describes an antiballistic structure comprising a front stand-off panel including an elastically deformable laminate matrix and a plurality of rigid elements supported therein. The rigid elements are means for absorbing the energy of the incident projectiles and for destabilizing them. The front panel is mounted on a deformable separator layer which is fixed on a main armor plate.

U.S. Pat. No. 4,398,446 discloses add-on armor arrangements designed for the attachment to a side wall of a military vehicle to provide different levels of ballistic protection. The difference in the arrangements is mainly in the number of armor layers and their location relative to the vehicle's side wall. In particular, in some arrangements where only one armor layer is used, it is mounted either directly or close to the vehicle's side wall or at a location spaced therefrom by spacers. In the arrangements where two armor layers are used, one of them is mounted directly or close to the vehicle's side wall while the other is mounted at a location spaced therefrom. In all the cases, each armor layer consists of tiles whose edges abut each other to define a substantially uninterrupted armor surface.

EP 1 128 154 describes a ballistic armor panel for attaching to an object, the panel comprising a carrying board made of a hard material such as steel and formed with a plurality of adjoining through-going holes. Each hole accommodates a body made of a hard material. The panel is mounted face to face with the protected object.

SUMMARY OF THE INVENTION

In this application, some terms will be used as follows:

Destabilization (of a projectile) is loss of stable orientation of the projectile axis along the flight trajectory as a result of a non symmetrical impact with a layer of material. The destabilization is measured by the yaw angle between the projectile longitudinal axis and the direction of the flight trajectory. The yaw angle increases the stopping power effectiveness of the armor system especially when the yaw angle exceeds 5°.

Characteristic diameter (of a projectile or an opening) is just the diameter, if the projectile or the opening is circular, or

diameter of the largest inscribed circle, in case of a non-circular opening; and

diameter of the smallest described circle, in the case of a projectile with non-circular cross-section (shrapnel or fragment);

Ballistic material is a hard material capable of penetration resistance.

Main armor plate is an armor plate mounted closest to the structure to be protected or resident therein. A wall of the structure may be also a main armor plate or part thereof.

In accordance with one aspect of the present invention, there is provided a system of armor plates for protection of a structure such as a vehicle against projectiles B and S of two characteristic calibers D_(B) and D_(S), D_(B) being larger than D_(S). The system comprises a main armor plate and an auxiliary armor plate mounted in front of the main armor plate at a distance L therefrom. The auxiliary plate is perforated with through holes of characteristic diameter D, D being larger than D_(S) up to about 1.2 D_(B). At least one hard-material body is fixed in each of the holes, so as to provide at least destabilization of impacting projectiles S or B capable of free passage through an unobstructed hole of diameter D when striking close to the hole center.

The space between the auxiliary armor plate and the main armor plate may be free or at least partially filled with a non-ballistic material, for example a honeycomb structure.

The auxiliary armor plate may be connected to the main armor plate by a plurality of metallic bolts, pins or brackets.

The system may be constructed of panels comprising the main armor plate and the auxiliary armor plate fixed at the distance L therefrom, the panels being adapted for mounting on the structure.

According to another aspect of the present invention, there is provided an auxiliary armor plate for use in the above system of armor plates, which auxiliary plate may be made of ballistic steel.

The holes in the auxiliary plate are preferably disposed with center to center spacing from 1.2 D to 1.9 D, preferably in a regular array.

The hard-material bodies may be made of ceramics and may be fixed in the holes by resin or metal.

The auxiliary plate may further comprise at least one front and/or rear layer of material bonded thereto so as to fix the hard-material bodies in the holes. The material may be fiberglass, aramid fabric, metallic sheet or other fiber fabric in resin matrix.

According to further aspect of the present invention, there is provided an add-on armor kit comprising the above auxiliary armor plate, an instruction for use thereof in a system of armor plates, and optionally, means for mounting the auxiliary armor plate on the protected structure.

The invention may be applied to various types of military vehicles and may provide combined ballistic protection against projectiles of different diameters ranging, for example from 7.62 mm, 0.5″ (12.7 mm), to 14.5 mm or even to 20 mm.

The armor having the main and auxiliary plates according to the present invention may have a lighter weight than the weight it would need to have in order to provide the same level of ballistic protection, if the armor consisted only of one plate or if the auxiliary plate had only through openings. Moreover, when used as an add-on armor on a vehicle's basic structure, the auxiliary armor plate of the present invention may allow a smaller distance to the basic structure, than the distance it would need to have for the same level of ballistic protection, with single plate armor of the same weight (perforated or not).

The above may be partially explained by the combined effect of:

the auxiliary plate with holes and hard bodies, which may cause a projectile of wide caliber range, when penetrating and impact the hard bodies of said auxiliary plate, to be deflected and to further be initially shattered or at least destabilized; and

the spacing between the auxiliary and the main plates, which allows the deflected projectile trajectory or destabilized projectile attitude to further deviate from a normal impact on the main plate, or allows the projectile's parts to be more separated in space between their impact on the main plate.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, an embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a ballistic armor in accordance with an embodiment of the present invention; and

FIG. 2 is a cross-sectional view of the armor shown in FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENT

An armor system 10 schematically shown in FIGS. 1 and 2 is an example of ballistic armor of the present invention designed for ballistic protection of a basic structure, e.g. side wall 12 of a vehicle, against two kinds of ballistic threats, for example, large caliber bullets B and smaller caliber bullets S.

The armor 10 comprises a main armor plate 14 and an auxiliary armor plate 16 located in front of the main armor plate 14. The plates 14 and 16 are attached to the side wall 12 by attachment means such as bolts 18 as shown in FIG. 1. Alternatively, the main armor plate 14 may be attached to the side wall 12 by one attachment means, and the auxiliary plate 16 may be attached to the main plate 14 or to the side wall by another attachment means. The attachment means are designed to keep the plates at a predetermined fixed distance (stand-off) from each other.

The main armor plate 14 is designed to stop alone, or together with the side wall 12 but without the auxiliary plate 16, projectiles of relatively small diameter D_(S) and penetration capability (lower level threats) such as 7.62 mm small arm bullets. The main plate may be a composite armor plate, for example comprising front layer 20 and a rear, backing layer 22 bonded to the front layer. The front layer 20 may comprise cylindrical pellets made of ceramics, for example alumina, held by synthetic resin. The rear layer 22 may be made of aluminum sheet, fiberglass, aramid fiber material such as Kevlar™, another fabric in resin, or a combination thereof. It should be understood that the side wall may be integral with the main armor plate or may be considered a main armor plate by itself, as a component of the armor system described herein.

The auxiliary plate 16 comprises a perforated plate which may be made of steel, titanium or aluminum and their alloys, or of carbon fibers and the likes in hard resin matrix. The perforated plate is formed with through holes 19 of diameter D, spaced from each other by a distance and arranged in a regular pattern.

The perforated plate with the holes 19 may be designed to deflect and shatter or at least destabilize by itself projectiles with relatively large diameter D_(B) which cannot be stopped by the main plate 14 alone or together with the side wall 12. For example, such projectiles may be 0.5″ to 14.5 mm machine-gun armor piercing bullets. The diameter D of the holes in this case is smaller than D_(B) but large enough to be felt by a projectile of diameter D_(B), when impacting the hole. The range of D then may be between D_(S) and D_(B), preferably 1.1 D_(S)<D≦0.9 D_(B). The total area of the holes 19 is preferably between 40% and 50% of the area of the perforated plate. For example, for bullets of 0.5″ or 14.5 mm caliber, holes of diameter D=11 mm may be used (in 8 mm thick plate), arranged in staggered rows, with centers disposed at 16 mm from each other.

In operation, a projectile B impacts the perforated plate and, while penetrating the plate, is deflected (its path is deviated from the normal flight direction thereof) and initially shattered or at least destabilized. The destabilized and deflected projectile or parts thereof, then impact the front layer 20 of the main plate 14, which further shatters the projectile or its parts into small fragments. The backing layer 22 absorbs and dissipates kinetic energy of the fragments on the protected side wall 12, at which the projectile is finally stopped.

However, the perforated plate alone, as described above, may be pierced by low caliber threats, such as the bullet of diameter D_(S), passing through the holes 19 when D>D_(S) without any influence to their trajectory. For example, a 7.62 mm bullet may pass easily through 11 mm dia holes. Although the main armor plate 14 will be usually capable to stop such low-level threat, sometimes a small-caliber threat may be an overmatch to the main armor plate. Such threat may be special armor-piercing munitions with WC (Tungsten Carbide) core, such as 7.62×51 mm API(WC)FFV, NAMMO, etc.

To avoid such situation, the present invention provides hard bodies of characteristic diameter D_(H) such as ceramic pellets 28 which are placed in the holes 19, as shown in FIG. 2, to augment the perforated plate and obtain the auxiliary plate 16. The bodies may be bonded in the holes, and the auxiliary plate may be covered at one or both sides by a thin layer of laminated fabrics 30 such as fiberglass, aramid, carbon or other fibers in hard resin etc. and/or metallic sheet such as aluminum sheet.

With such arrangement, the low-caliber threat S will impact either the auxiliary plate 16 or one of hard bodies 28 and will be shattered, or at least destabilized, losing great deal of its penetrating capability. The operation of the armor 10 against the large-caliber projectile B will be at least the same as the perforated plate without the hard bodies, or even may have improved performance.

Although this solution will raise somewhat the areal density (weight) of the auxiliary plate of given thickness, it will enhance its performance and efficiency. The eventual effect will be that the overall weight may be reduced, for example 8 mm thick steel auxiliary plate with ceramic bodies will be equivalent to 10 mm thick steel perforated plate that still cannot affect all low-caliber special threats (for example, WC core). Moreover, the inventors have found that adding fixed hard bodies in the holes allows making the holes larger without losing the antiballistic effect against the higher-caliber threat B. The diameter D of the hole may be made as large as about 1.2 D_(B). Those projectiles B that hit close to the hole center are shattered by the impact into the hard body. It will be appreciated that, especially with larger holes, the diameter D_(H) of the hard bodies is preferably not less than the difference between D and D_(S), i.e. not less than D−D_(S) in order to avoid penetration of low-caliber threat S if the hard body is bonded off-center. Thus, the usage of larger holes allows further reducing the weight of the auxiliary plate, especially if made of steel, as the ceramic bodies have lower specific weight than steel.

The perforated plate for the auxiliary plate 16 may be made of metallic or non metallic materials such as ballistic steel of various grades, titanium, aluminum alloys, hard fibrous material plates or laminates etc, by drilling, milling, punching, laser or water jet cut, etc.

The armor 10 may be produced as a module with the auxiliary plate 16 fixedly attached to the main plate. The module may be provided with means for mounting on the vehicle side wall 12, which may be protected by a number of such modules. Alternatively, the auxiliary plate may be produced separately as add-on plate and mounted at a vehicle manufacturer facility or at an armor-specialized workshop. Also, the auxiliary plate may be offered in a kit with means for mounting and instructions for mounting on a vehicle with given basic armor and required ballistic protection level.

Although a description of specific embodiments has been presented, it is contemplated that various changes could be made without deviating from the scope of the present invention as defined in the following claims. For example, the holes in the auxiliary plate may be of non-circular form but polygonal, elliptic or extended like slits. The space between the two plates may be empty or filled by a spacing layer of non-ballistic material such as wood, plastic or light metal layer which may be formed as porous foam or honeycomb, etc. 

1. A system of armor plates for protection of a structure against projectiles B and S of two characteristic calibers D_(B) and D_(S), D_(B)>D_(S), the system comprising a main armor plate and an auxiliary plate mounted in front of said main armor plate at a distance (stand-off) therefrom, wherein said auxiliary plate comprises a perforated plate made of ballistic material and perforated with through holes of characteristic diameter D, 1.2 D_(B)>D>1.2 D_(S), and at least one hard-material body disposed in each of said holes, such that said auxiliary plate provides at least destabilization of impacting projectiles S capable of free passage through an unobstructed hole of diameter D.
 2. The system of claim 1, wherein said body has diameter D_(H) which is not less than D−D_(S).
 3. The system of claim 1, wherein said auxiliary armor plate is connected to said main armor plate by a plurality of metallic bolts or pins or brackets.
 4. The system of claim 1, wherein the space between said auxiliary armor plate and said main armor plate is free.
 5. The system of claim 1, wherein the space between said auxiliary armor plate and said main armor plate is at least partially filled with a non-ballistic material.
 6. The system of claim 5, wherein said non-ballistic material is a honeycomb structure.
 7. The system of claim 1 constructed of panels comprising said main armor plate and said auxiliary armor plate fixed at said stand-off therefrom, said panels being adapted for mounting on said structure.
 8. An armor panel for constructing the system of claim 1, said panel comprising said main armor plate and said auxiliary armor plate fixed at said distance L therefrom, said panel being adapted for mounting on said structure.
 9. An auxiliary armor plate for use in a system of armor plates for protection of a structure against projectiles B and S of two characteristic calibers D_(B) and D_(S), D_(B)>D_(S), the system further comprising a main armor plate, said auxiliary armor plate being adapted for mounting in front of said main armor plate at a distance therefrom, wherein said auxiliary plate comprises a perforated plate made of ballistic material and perforated with through holes of characteristic diameter D, 1.2 D_(B)>D>1.2 D_(S), and at least one hard-material body disposed in each of said holes, so that said auxiliary plate provides at least destabilization of impacting projectiles S capable of free passage through an unobstructed hole of diameter D.
 10. The auxiliary plate of claim 9, wherein said body has a diameter D_(H) which is not less than D−D_(S).
 11. The auxiliary plate of claim 9, wherein said carrying plate is made of ballistic steel.
 12. The auxiliary plate of claim 9, wherein said holes are disposed with center-to-center spacing from 1.2 D to 1.9 D.
 13. The auxiliary plate of claim 12, wherein said holes are disposed in a regular array.
 14. The auxiliary plate of claim 10, wherein said hard-material bodies are made of ceramics.
 15. The auxiliary plate of claim 10, wherein said hard-material bodies are fixed in said holes by plastic resin or aluminum.
 16. The auxiliary plate of claim 9, further comprising at least one front and/or rear layer of material bonded thereto so as to fix the hard-material bodies in said holes.
 17. The auxiliary plate of claim 16, wherein said at least one layer is one or more of the following: fiberglass, aramid fabric, metallic sheet, carbon or other fibers in hard matrix.
 18. An add-on armor kit comprising the auxiliary armor plate of claim 9 and an instruction for use thereof in said system of armor plates.
 19. The add-on armor kit of claim 18, further comprising means for mounting said auxiliary armor plate on said structure. 